Experts said a significant factor in the shift was a shift in attitudes towards sex, meaning that more women were willing to report having had multiple partners.

Prof Dame Anne Johnson of University College London, one of the study's leaders, said: "I think the whole dynamic of male-female relationships has changed over the past 60 years.

"It is reflecting how essentially women are now in a position of being able to have sexual lifestyles that are much more similar to men and are accepted by both sides."

There is also evidence that women in particular have become more open to same-sex experiences, with 16 per cent today having had at least one such experience, including kissing, compared with four per cent in 1991.

In contrast the rate of same-sex encounters among men rose from six per cent to seven per cent over the same period.

The figures were published as part of the National Survey of Sexual Attitudes and Lifestyles (Natsal), a major study conducted in Britain every decade.

Researchers questioned more than 15,000 adults aged 16 to 74 on subjects including their sexual behaviour, attitudes, health and well-being.

People today are more sexually adventurous and are more accepting of same sex relationships but have become more critical of extramarital affairs and one-night stands, figures published in The Lancet showed.

Three in ten young people today first had sex before the age of 16, and that people continue having sex into their seventies with 60 per cent of men and 40 per cent of women aged 65 to 75 still sexually active.

Some 40 per cent of men and 50 per cent of women report having experienced at least one or more problems with sexual function, such as a lack of libido, anxiety or functional problems.

The survey also revealed that one in ten women has been made to have sex against their will, and that one in every six pregnancies in Britain is unplanned.

Some 16 per cent of women were found to have the HPV virus, a sexually transmitted virus which causes cervical and other cancers, while about 3.1 per cent of women and 2.3 per cent of men aged 16 to 24 had chlamydia.

Prof Kaye Wellings of the London School of Hygiene and Tropical Medicine, another of the authors, said: "With three surveys and an age range of 16 to 74 we can take longer view and look at some generational changes over half a century.

"We see striking changes in the timing of events relating to sexual and reproductive health. We do see a progressive decrease in onset of sexual activity and at the same time we see an increase in time of first cohabitation and becoming a parent.

"Because those intervals have increased, the length of time during which people are more at risk of adverse sexual health outcomes has increased."